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Balanced outputs and inputs from modular to audio interface?
MUFF WIGGLER Forum Index -> Modular Synth General Discussion Goto page 1, 2  Next [all]
Author Balanced outputs and inputs from modular to audio interface?
bennelong.bicyclist
I'm seriously contemplating purchase of an audio interface and a DAW to use with my Digisound-80 modular (and a planned collection of Mutable Instruments devices, yet to be built and/or acquired). The DAW will be Logic Pro X (I only use Macs, and given that capabilities of Logic X, the value is unbeatable) and the audio interface will be a Behringer FCA1616 (adequate quality for my purposes, has an ADAT interface for potential future use with an Expert Sleepers ES-3, has 8 line inputs, and is also great value) - see http://www.behringer.com/EN/Products/FCA1616.aspx

The Behringer documentation (such as it is) says:

"[Rear] inputs are balanced 1/4" jacks that accept a wide range of line-level devices. Outputs accept both balanced and unbalanced 1/4" connections."

The four front inputs appear to be balanced combination XLR/6.35mm TRS jack sockets for either mic or line inputs.

OK, here are my naive questions: what do I need to connect output from my Digisound modular, which uses 3.5mm unbalanced line level sockets, with signals nominally up to 10V p-p? Will I need a balun or DI device to convert the unbalanced line-level signals from the synth into balanced line-level input for the audio interface? If so, what type (and recommendations?)? Obviously I'll need suitable interface cables. Recommendations?
Nantonos
So you need a module which takes one (or more) modular-level unbalanced inputs and gives you one (or more) pro line level (+4dBU) balanced outputs, either on 1/4" TRS jacks or on 3-pin XLR. There are various options depending on how manch channels you want; some also give you audio inputs as well (mic or line level).

The one I use is the Pulp Logic Exit strategy which provides a single balanced out on 1/4" TRS with adjustable level, optional limiter, and post-limiter output level metering.

To get two line level balanced outs, you could look at WMD Pro Output. Or if you want inputs as well as outputs, the Intellijel Audio Interface
gives two inputs, two outputs, with metering on each channel.

All of these are using electronic balancing. Transformer coupling of good quality will be more expensive, and is usually used when people want to deliberately overdrive the transformers for colour. An example would be the ADDAC800X High-End Outputs which provides two transformer-balanced outputs on XLR, with no metering.

Cables are standard line level balanced cables, TRS to TRS or XLR to TRS as appropriate. You can get those from any music shop in various lengths from 50cm to 20m.
Dave Peck
Although you can get those functions in a specialty module that gets installed in your modular synth, it should be easier and cheaper to just get a couple of decent quality active direct boxes. Go to any site that sells pro audio gear (sweetwater.com, musiciansfriend.com, vintageking.com) and do a search on the phrase 'active direct box'. Pick from any reputable manufacturer like Radial, Whirlwind, or Countryman.
bennelong.bicyclist
Dave Peck wrote:
Although you can get those functions in a specialty module that gets installed in your modular synth, it should be easier and cheaper to just get a couple of decent quality active direct boxes. Go to any site that sells pro audio gear (sweetwater.com, musiciansfriend.com, vintageking.com) and do a search on the phrase 'active direct box'. Pick from any reputable manufacturer like Radial, Whirlwind, or Countryman.


OK, thanks, but I've subsequently learnt that an unbalanced 1/4 inch jack can be plugged into a balance TRS 1/4 inch socket and it will just work (albeit without noise cancellation), albeit with 6dB of signal loss - but typical modular synth levels are pretty high in any case. However, I'll bear in mind the possibility that some active direct boxes may be required. Many thanks for the advice, much appreciated.
bennelong.bicyclist
Nantonos wrote:
So you need a module which takes one (or more) modular-level unbalanced inputs and gives you one (or more) pro line level (+4dBU) balanced outputs, either on 1/4" TRS jacks or on 3-pin XLR. There are various options depending on how manch channels you want; some also give you audio inputs as well (mic or line level).

The one I use is the Pulp Logic Exit strategy which provides a single balanced out on 1/4" TRS with adjustable level, optional limiter, and post-limiter output level metering.

To get two line level balanced outs, you could look at WMD Pro Output. Or if you want inputs as well as outputs, the Intellijel Audio Interface
gives two inputs, two outputs, with metering on each channel.

All of these are using electronic balancing. Transformer coupling of good quality will be more expensive, and is usually used when people want to deliberately overdrive the transformers for colour. An example would be the ADDAC800X High-End Outputs which provides two transformer-balanced outputs on XLR, with no metering.

Cables are standard line level balanced cables, TRS to TRS or XLR to TRS as appropriate. You can get those from any music shop in various lengths from 50cm to 20m.


Thanks! I'll bear all those in mind when I start a Eurorack, which is inevitable in 2014, I fear.
slow_riot
Most people don't understand balancing. In an analogue system, audio is generally represented as a voltage which is an energy potential between 2 points and requires a positive voltage and a zero voltage. In an unbalanced system the zero voltage is also used for shielding and safety... so any noise that gets onto your 0V will be seen as noise or hum.

A balanced system alleviates this problem by using 3 connections per cable to get from different pieces of audio gear, and it uses circuitry to ensure that most noise that appears on the +ve and 0V connections is removed.

An electronically balanced output (or impedance balanced) actually costs the same as an unbalanced one really... or pennies different, and does everything that you would require it to do. The complex part is in the receiver circuitry on a balanced input that cancels any noise that is common on your +ve and 0V connections.

You certainly don't need to spend £500 on a transformer balanced output (and if you look at the specs of the noise removed from a transformer balanced O/P you will ask yourself why the designer bothered).

Unless you are trying to drive a long distance of cable a simple electronically balanced O/P would suffice... Hinton and Wiard understand this and you can use their equipment very easily to interface with balanced inputs and outputs without needing a special output module.
slow_riot
With the digisound you can use the balanced input with an unbalanced output and still get some of the noise rejection that the balanced receiver is doing. More so if you use a balanced cable and connect the cold/ring connection to the shield/ground connection at the unbalanced end.
ear ear
If you want a clearer understanding of what balanced connections do and don't do, search for posts by Graham Hinton. Lots of other useful information in his posts as well.
Dave Peck
bennelong.bicyclist wrote:


OK, thanks, but I've subsequently learnt that an unbalanced 1/4 inch jack can be plugged into a balance TRS 1/4 inch socket and it will just work (albeit without noise cancellation), albeit with 6dB of signal loss - but typical modular synth levels are pretty high in any case. However, I'll bear in mind the possibility that some active direct boxes may be required. Many thanks for the advice, much appreciated.


Yes, you should first try just plugging it right into the mixer and in most cases it will work just fine. All of the discussion about direct boxes etc. is what you might do in case it does NOT work fine and you're not able to troubleshoot a hum problem. If you don't have a hum problem, or a level problem that can't be addressed with the trim controls, you don't need any special adapter to fix anything.
Nantonos
bennelong.bicyclist wrote:
Nantonos wrote:
So you need ...


Thanks! I'll bear all those in mind when I start a Eurorack, which is inevitable in 2014, I fear.


d'oh! that 'not noticing you are not in the Euro forum' feeling. Sorry.
The parts about recommending electronically balanced outputs, not needing transformers unless you want transformer colouration, and using balanced cables, still stand though.
PrimateSynthesis
Balanced is for only two things, low level signals such as microphones, and long cable runs.

Considering Behringer, and problems people have reported with modulars overloading prosumer converters, you might want that 6 dB loss meh

In over thirty years of hooking things up, only once did I have a problem with an unbalanced synth output going into a balanced TRS input with just a regular 1/4" TS cable. There was a hum when I had a Mini Moog across the room from a mixer. While it was probably do to some undiagnosed problem, I took the lazy way out and used a TS/XLR isolation transformer adapter I had, and it went away.

This is an excellent reference:

http://www.rane.com/note110.html

Generally, it's best to work backwards. Start with a regular TS cable. If it works, you're done. Then try a telescoping cable (which might end up getting mixed up with your other cables if you don't label it d'oh! ) Then try things like floating, transformers, etc. Starting with the technically "best" solution is usually a waste of time an money. Also consider that transformers, match boxes, etc. are not perfect devices and can effect the sound. There is nothing cleaner than a straight wire if it works.
slow_riot
I've been doing quite a lot of studying recently into this subject. I acquired a late 80s PA system that was generally built to very high standards but was completely unbalanced. When I received it, the active crossover unit had it's safety earth connection disconnected from the signal common, but in the interest of safety I put in this connection. This created around 50-60dB of 50hz sine wave on the output, not very pleasant at all! Even when using cable runs as short as 15cm.

By adding transformer balanced inputs to the power amplifiers, and impedance balanced outputs to the active crossover, this noise was completely gone.

I believe very strongly that balancing is very crucial in audio systems. You can get away without balancing in equipment that is unsafely connected by removing earth connections, but that is not a solution that is fair to the operators of the machinary or anyone else that is involved in setting it up or being near it. Proper safe connection with balancing also allows the use of the earth connection as a shield for more removal of noise.

Absolutely no alternative IMHO... it's not a corner that I am willing to cut and it adds what, 5-10% to the cost of the equipment to do it safely and properly.

Also, in the context that the OP mentioned, it won't actually be possible to use an unbalanced connection without tampering with the device. The balanced receiver circuitry on the soundcard will still balance the input even if used with an unbalanced output, though not with quite the same results as a proper balanced output.
Graham Hinton
PrimateSynthesis wrote:
Balanced is for only two things, low level signals such as microphones, and long cable runs.


Three things: between equipment powered with different mains power supplies. i.e. between a modular and anything else or within a modular once it is big enough to need two PSUs.

Get out of the mindset that balanced is unnecessary and into the mindset that using unbalanced is only a temporary solution for small systems. Everybody accumulates more and more gear so sooner or later a transition has to be made.

Quote:

This is an excellent reference:

http://www.rane.com/note110.html

Generally, it's best to work backwards. Start with a regular TS cable.


That advice is contrary to the document you just referred to and to the AES standard.
It is better, and cheaper in the long run, to start with a balanced wiring scheme and unbalance it where necessary for unbalanced equipment. The difference in cost between screened twisted pair and single core cable is small and the labour cost to wire up either is greater. Twisted pair may be used for either, but single core has to be replaced.

Cabling is a significant investment and should be budgeted at 25% to 35% of the equipment value it is used with. When done right it will last longer than the equipment. If an unbalanced FX unit is upgraded to a better balanced one then only the connectors will require changing if twisted pair cabling is already in place.

Quote:

Then try a telescoping cable (which might end up getting mixed up with your other cables if you don't label it d'oh! )


This is a deprecated practise, like disconnected Earths on mains plugs. All cables should have a continuous screen. Bodging a solution may appear to fix it, but it only moves the problem elsewhere to be found later--normally at the most inconvenient time to deal with it. If anything really needs to be disconnected it should be done inside the equipment being connected, preferably by the designer.
PrimateSynthesis
Graham Hinton wrote:

Three things: between equipment powered with different mains power supplies. i.e. between a modular and anything else or within a modular once it is big enough to need two PSUs.

Get out of the mindset that balanced is unnecessary and into the mindset that using unbalanced is only a temporary solution for small systems. Everybody accumulates more and more gear so sooner or later a transition has to be made.


Sorry, but that simply isn't true. You are describing an unnecessary solution for a future problem that might not ever happen.

Graham Hinton wrote:

That advice is contrary to the document you just referred


Yes, it is. They are describing the "best" way first. Which is generally unnecessary. Skip down to the part about cabling connectors.

Graham Hinton wrote:

It is better, and cheaper in the long run, to start with a balanced wiring scheme and unbalance it where necessary for unbalanced equipment. The difference in cost between screened twisted pair and single core cable is small and the labour cost to wire up either is greater. Twisted pair may be used for either, but single core has to be replaced.


I think we have a misunderstanding here. I am not suggesting that balanced equipment should be connected unbalanced. You can take that up with George Massenburg hihi

In all the PA's and studios I've built, I've never wired it unbalanced. That would silly, since most pro gear is balanced.

What I am saying, is that unbalanced synth or line-level equipment generally doesn't need to be electronically or transformer balanced before being connected a short distance to a balanced input. Like I said, nothing is cleaner than a straight wire if it works.

Imagine taking your advice to its logical extreme. Would you balance all the individual outputs of a 808 or 909 going into a mixer? In spite of countless recordings, I've never heard of anyone ever doing that. In the late 80's you couldn't leave the house without seeing a DX7 on stage. And I don't ever remember seeing a direct box hanging off one.

Graham Hinton wrote:

This is a deprecated practise, like disconnected Earths on mains plugs. All cables should have a continuous screen. Bodging a solution may appear to fix it, but it only moves the problem elsewhere to be found later--normally at the most inconvenient time to deal with it. If anything really needs to be disconnected it should be done inside the equipment being connected, preferably by the designer.


No, it isn't. For example, a telescoping cable is often the best solution when going from a guitar to A/D converter with balanced instrument inputs. The same applies to unbalanced microphones (eg. pzm, green bullet) going into a balanced pre. Although I do agree it is unlikely a good practice with a hot signal. But if something else is wrong, and there is ground loop, or if it's a RF hostile environment, sometimes snipping a shield or a telescoping cable is the way to get things done.

Nor would I ever recommend disconnecting ground on power connectors. That being said, I've done it in live situations because the show must go on. But that doesn't mean you should do it Dead Banana
Graham Hinton
PrimateSynthesis wrote:

Sorry, but that simply isn't true. You are describing an unnecessary solution for a future problem that might not ever happen.


What isn't true? People don't buy more and more gear and then into problems? I'm describing a necessary solution for a present or future problem that will happen.

Quote:

What I am saying, is that unbalanced synth or line-level equipment generally doesn't need to be electronically or transformer balanced before being connected a short distance to a balanced input.


It doesn't need to be transformer isolated unless the design is really bad, but electronically balanced costs virtually nothing. If you buy one of the cheapest 4 channel mixers, like £35 discount after a shop, distributor and manufacturer have made a profit, it will have balanced I/O so there is no excuse for equipment costing orders of magnitude more not doing it.

Quote:
Like I said, nothing is cleaner than a straight wire if it works.


The operative word in that sentence is if. A straight wire only "works" if its resistance is small enough to be negligible and both ends have a common reference and that is only the case within equipment. As soon as you connect two unbalanced pieces of equipment together you are causing currents to flow in screening and earth wiring where it should not be. The more gear is added the more hash gets into the common reference and at some point will become unacceptable.

Quote:

Would you balance all the individual outputs of a 808 or 909 going into a mixer?


If it were being made now, yes, I would make them pseudo balanced (like most small mixers) for balanced/unbalanced compatibility. We are not in the 80s anymore. Since then rafts of non-harmonised legislation on safety and EMC have been introduced that manufacturers have to comply with to sell to a world market.

Quote:
In the late 80's you couldn't leave the house without seeing a DX7 on stage. And I don't ever remember seeing a direct box hanging off one.


Most stages, even in small clubs, have transformers built into stage boxes. Just because it isn't visible doesn't mean if isn't there. They have learnt that they have to protect themselves from the problems that unbalanced equipment on stage cause.

Quote:

For example, a telescoping cable is often the best solution when going from a guitar to A/D converter with balanced instrument inputs. The same applies to unbalanced microphones (eg. pzm, green bullet) going into a balanced pre.


That's exactly the sort of bodging I'm talking about. It only works one way for one particular combination and when that changes you have to find another fix. In both the cases you cite telescoping (i.e. disconnected ground one end) is not the correct solution, it should be a screened twisted pair with cold and screen connected together at the unbalanced end. If that causes a problem it would indicate improper wiring of the pre input connector, like XLR pin 1 to signal ground as the Rane note discusses.

Quote:

But if something else is wrong, and there is ground loop, or if it's a RF hostile environment, sometimes snipping a shield or a telescoping cable is the way to get things done.


Modern EMC practise will form ground loops. Attacking them without seeing the big picture is bad practise. I know people do it, but those people rarely pick up their shit afterwards. There's a difference between doing it in desperation knowing it is wrong and advocating it as recommended practise. In decades of experience in recording studios and live work I have never ever had to snip an earth, but many times I have had to reconnect ones that somebody who did not know what they were doing had removed. The state of gear brought in by bands and from hire companies was often literally shocking.
PrimateSynthesis
Graham Hinton wrote:

What isn't true?


That you need balanced between equipment powered with different mains power supplies. i.e. between a modular and anything else or within a modular once it is big enough to need two PSUs. People do it all the time without a problem.

Graham Hinton wrote:

It doesn't need to be transformer isolated unless the design is really bad, but electronically balanced costs virtually nothing. If you buy one of the cheapest 4 channel mixers, like £35 discount after a shop, distributor and manufacturer have made a profit, it will have balanced I/O so there is no excuse for equipment costing orders of magnitude more not doing it.


Oh, I'm not talking about designing equipment.

Graham Hinton wrote:

Most stages, even in small clubs, have transformers built into stage boxes. .


Even then it's still run unbalanced to that box. And often a distance longer than you might have in a studio.

Graham Hinton wrote:

That's exactly the sort of bodging I'm talking about. It only works one way for one particular combination and when that changes you have to find another fix. In both the cases you cite telescoping (i.e. disconnected ground one end) is not the correct solution, it should be a screened twisted pair with cold and screen connected together at the unbalanced end. If that causes a problem it would indicate improper wiring of the pre input connector, like XLR pin 1 to signal ground as the Rane note discusses.


Then I suggest we agree to disagree on that.
slow_riot
PrimateSynthesis wrote:

Even then it's still run unbalanced to that box. And often a distance longer than you might have in a studio.



using a special cable that bypasses the fact that transformers are inherently balanced?
slow_riot
PrimateSynthesis wrote:


That you need balanced between equipment powered with different mains power supplies. i.e. between a modular and anything else or within a modular once it is big enough to need two PSUs. People do it all the time without a problem.


Don't know how much that is true. PSUs from 2 of the biggest modular manufacturers are aware that this is a problem and have disconnected the earth pins as part of the design to "correct" this.
os
bennelong.bicyclist wrote:
what do I need to connect output from my Digisound modular, which uses 3.5mm unbalanced line level sockets, with signals nominally up to 10V p-p?

You mentioned the ES-3 in your post - get an ES-6 too and you can run regular patch cables to the ES-6 and then ADAT back to the interface.
memes_33
having been building a eurorack modular system to add to my existing production studio, i did several tests on the best way to record my modular with my current system. although these are simple test and some issues might be unique to my specific set-up, here is what i found worked best for me in terms of signal to noise.

i set up my modular to output white noise from my blue lantern noise generator. i sent that noise out direct from the source, as well as through my pittsburgh modular In/Out via 1/4". i sent the signal out to my apogee duet audio interface, and tried the various input signal types (mic, -10dB line, +4dB line). i used both 10K:10K and 600:600 transformers from Edcor and my passive radial JDI box. i used Roger Nichol's Inspector plugin to compare the signals; i would adjust levels to get -1dB on the inspector meters, then disconnect the signal from the noise module to compare the noise. i also visually noted the frequency response coming in.

my best results where noise>pittsburgh in/out>JDI>apogee mic level XLR inputs. best signal/noise ratio, and at least as flat in frequency response as the other options, possibly flatter than some (can't remember details at this time- notes at home and i'm at work).

not sure why an active DI was suggested over a passive one, but i personally love the sound of the JDI's jensen transformers and, given that modular levels are pretty high, the additional boost from an active DI isn't really needed IMO.

i should note that one reason the JDI did so much better than the Edcor 10K:10K is the edcor transformer was picking up a lot of low-frequency noise from somewhere. i was never able to get rid of it, but i was able to make it go down/up by simply moving the transformer's physical location (the box with the transformer inside, not the transformer within the box).

my $0.02...
PrimateSynthesis
slow_riot wrote:
PrimateSynthesis wrote:

Even then it's still run unbalanced to that box. And often a distance longer than you might have in a studio.



using a special cable that bypasses the fact that transformers are inherently balanced?


I meant unbalanced from the synth to the box.
Graham Hinton
PrimateSynthesis wrote:
People do it all the time without a problem.


Plenty of people have problems and some don't know that this is the cause of their problems.

Quote:

Even then it's still run unbalanced to that box. And often a distance longer than you might have in a studio.


It's run differential into the box even though one side may happen to be grounded. Distance is a matter of output impedance and current drive and most keyboards are quite capable of driving more than 2m.

Quote:

Then I suggest we agree to disagree on that.


We can. What you are advocating was common practise in the 80s, but has been rendered incorrect by EMC compliance which came in mid-90s. Most 80s synthesizers and drum machine, full of microprocessors and digital circuitry, would not pass EMC regulations now. Disconnecting the shield at one end diminishes the screening at RF and may form an aerial picking up more RF. The equipment being connected may have RF decoupling to the shield which would be made ineffectual.



memes_33 wrote:
i should note that one reason the JDI did so much better than the Edcor 10K:10K is the edcor transformer was picking up a lot of low-frequency noise from somewhere. i was never able to get rid of it, but i was able to make it go down/up by simply moving the transformer's physical location (the box with the transformer inside, not the transformer within the box).


This is because the transformer is not magnetically screened so it acts as a pickup coil. Better transformers have mumetal shields, but they are expensive so expect to pay in the order of £100 for a DI containing one, e.g. EMO which use Sowter transformers in mumetal cans. Normal metal boxes only screen electric fields, magnetic fields pass through.

The real reason for using a DI box is to go into the mic inputs of a mixer, it may happen to reduce a hum problem or it may introduce one.
PrimateSynthesis
Graham Hinton wrote:

It's run differential into the box even though one side may happen to be grounded. Distance is a matter of output impedance and current drive and most keyboards are quite capable of driving more than 2m.


Yes, but as you do know, distance is a factor regarding noise (interference, greater chance of a difference in ground potential, etc.)

Although that still isn't balanced. Even in this rather hypothetical example, noise is being injected into the signal to avoid a possible problem.

So, imho, if running it straight were causing a problem, a better solution is to run it single-sided to a mixer, matchbox, etc. then balanced out of that to the house.

Graham Hinton wrote:

What you are advocating was common practise in the 80s, but has been rendered incorrect by EMC compliance which came in mid-90s. Most 80s synthesizers and drum machine, full of microprocessors and digital circuitry, would not pass EMC regulations now. Disconnecting the shield at one end diminishes the screening at RF and may form an aerial picking up more RF. The equipment being connected may have RF decoupling to the shield which would be made ineffectual.


Shields generally work grounded at one end. And yes, it was a common practice to float the sends and tie the returns on patch bays. The difference between theory and practice, is that in theory they are the same, but in practice they aren't. If you wire a 520 with the signal ground tied to the shield it's going to hum. Guitars have their own problems (cable capacitance, pots bleeding, etc.) In my book, pretty much any unpowered gizmo that isn't connected to ground otherwise (eg. a mic with the shield wired only to the chassis) is telescoping if it's wired balanced.


Graham Hinton wrote:

The real reason for using a DI box is to go into the mic inputs of a mixer, it may happen to reduce a hum problem or it may introduce one.


Exactly It's peanut butter jelly time!

slow_riot wrote:

Don't know how much that is true. PSUs from 2 of the biggest modular manufacturers are aware that this is a problem and have disconnected the earth pins as part of the design to "correct" this.


Really? Who? I don't know of any modular that distributes chassis ground. Anyway, I don't see how that could help unless the PSU was mounted to the same metal rails. Regardless, connecting the chassis of the power supply to the AC ground increases safety.
Graham Hinton
PrimateSynthesis wrote:

Yes, but as you do know, distance is a factor regarding noise (interference, greater chance of a difference in ground potential, etc.)

Although that still isn't balanced. Even in this rather hypothetical example, noise is being injected into the signal to avoid a possible problem.


It is too easy when discussing topics like this to generalise without qualifying and quantifiying the subject. Noise is a function of source impedance and you would need miles of cable, i.e. > 100 ohms, before it started to make a significant contribution compared to the output impedance and the noise floor of the signal. Interference cancellation is achieved by TP cable and a differential input, the source circuit does not effect it. Interference is caused by magnetic fields inducing a current into the impedance of the source and destination in parallel and you need a very strong field to produce a significant voltage in, say, 150 ohms. The theory of cancellation assumes that each wire picks up equal field which it doesn't in practise if the source is close to the cable, even so you can expect at least 40dB reduction on a signal that isn't very large to start with. Differential ground potentials are caused by currents flowing in the shields and again how much current and induced voltage are we talking about and where is it coming from?

Quote:

Shields generally work grounded at one end. And yes, it was a common practice to float the sends and tie the returns on patch bays. The difference between theory and practice, is that in theory they are the same, but in practice they aren't. If you wire a 520 with the signal ground tied to the shield it's going to hum.


That's old practise. Shields shouldn't be connected to signal common, but to chassis ground, signal common will also be connected to chassis ground, but only at one point. Before the '90s, when they didn't have wi-fi, bluetooth, mobile phones and UTP networks to contend with, equipment was often made with the cable shield input connected to the signal common of an input. That could cause a problem sometimes (apparently) solved by disconnecting a shield in the cable, but the modern practise is to connect the shield to chassis ground immediately on the panel connector.

Quote:

In my book, pretty much any unpowered gizmo that isn't connected to ground otherwise (eg. a mic with the shield wired only to the chassis) is telescoping if it's wired balanced.


That isn't telescoping. Telescoping is disconnecting the shield in one end of a cable run, rather than inside the equipment, i.e. deliberately removing a connection that is intended to be there. Now the aim is to create a shield over an entire system like a continuous skin without using this to conduct signals. My philosophy is to modify older equipment to bring it in line with modern practise and never to cut shields in free cables or even consider it as a viable option.
PrimateSynthesis
Graham Hinton wrote:

That isn't telescoping. Telescoping is disconnecting the shield in one end of a cable run, rather than inside the equipment, i.e. deliberately removing a connection that is intended to be there. Now the aim is to create a shield over an entire system like a continuous skin without using this to conduct signals. My philosophy is to modify older equipment to bring it in line with modern practise and never to cut shields in free cables or even consider it as a viable option.


Then I think it's a matter of being dividing by a common language. Telescoping is an adjective, for something wired as previously described, often deliberately by design with no disconnecting required. Disconnecting a ground, regardless whether it was planned or a makeshift effort, is typically called floating.
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